I have gotten numbers using xfx that indicate guard traces do work. More
importantly, I have seen positive effects on real boards. It is not important
to via to ground every "X" intervals of distance. It is critical that the
"guard traces" are grounded at the source and receiver. It is also necessary
for the guard traces to via whenever the signal does. For instance, if you have
a clock trace that vias from layer 1 to layer 4 and is routed as
ground-signal-ground (GSG), the ground (guard) trace should via from layer 1 to
layer 4 very closely.

See below for some quick results. Compare numbers in bold for effects on
crosstalk.

**** To unsubscribe from si-list or si-list-digest: send e-mail to
majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****